1. Field of the Invention
The present invention relates to a LED lamp string controller, more particularly relates to a synchronous lamp string controller applied in the synchronization of a LED lamp string.
2. Description of the Related Art
Lamp string has been widely applied as used in, for example, Christmas lamp, landscape lamp, and building lamp. Along with the progress of light emitting diode (LED) process and lower prices of LED products, application of LED in lamp string has become a trend. While LED is basically suitable for DC power and lamp string is applied in the AC power environment, there have been some lamp string products that use LED in the market. However, how to achieve synchronous changing presents a challenge in the application of LED lamp string. The present invention has studied this subject and obtained solid result, thereby submitting the patent application.
Current LED lamp string employs prior art as shown in FIG. 20, FIG. 21 and FIG. 23, wherein each light emitting module represents a set of RGB (three-colored) LED module. In the prior art, the technique shown in FIG. 1 is the most undesirable, for the lamp employs DC parallel type where all LED modules are arranged in parallel, which consumes greater current. That is, in order to supply greater current, the power adapter is structurally more complicated, or is more costly. The number of LED modules that can be parallelly arranged is also limited.
The technique shown in FIG. 21 is better than the technique shown in FIG. 1. Because the LED module is serially connected, the current consumption is smaller. As such, the power adapter is easily handled and hence costs less. But this technique still has a drawback, that is, the number of LED modules that can be serially connected is limited, subject to the DC voltage supplied by the power adapter, i.e. the higher the DC voltage, the more LED modules can be in series connection.
The technique shown in FIG. 22 is the best method among the three, in which the power adapter shown in FIG. 21 is replaced by a plurality of small power adapters, which are structurally relatively simple. In addition, there is no limit to the number of lamp units that can be connected. The only drawback is that because each LED module needs to be coupled with a small power adapter, the product cost tends to be higher.
In the prior art shown in FIG. 20, FIG. 21 and FIG. 22, a conventional LED module includes a red light emitting diode (R LED), a green light emitting diode (G LED), a blue light emitting diode (B LED) and a control circuit, as shown in FIG. 23. Two pins of the conventional LED module are connected externally to the positive and negative terminals of the DC power, respectively. The control circuit can be realized as an integrated circuit (IC), which is used to drive the three primary-colors RGB LED or mix the colors according to the procedure configured in the original circuit. However, the drawback of the conventional LED module is that they are embedded with discrete control ICs. As such, when the LED modules are used in a lamp string, the color changing of each LED module after power on is independently operated without synchronization. If each LED module is arranged with a controller and the controllers are synchronized, the effect shown by the lamp string will be quite different from the star-studded effect achieved by discrete LED modules. Thus, how to control product cost while achieving synchronization effect provides a direction for research and development.